Opposites are also illusion. The opposite inevitably is only 'slightly different' from its 'subject.' The face in the mirror is 'unfamiliar,' but certainly not inverted. Polarity is of interest only when it is examined without a third point for reference. 'Formal' concerns are not in any way 'pure,' they are the 'realization' that all 'purity' is imaginary, worthwhile, transparent.